Influence of stent length and heparin coating on platelet activation: A flow cytometric analysis in a pulsed floating model

Platelets are involved in acute and subacute thrombotic occlusions of coron ary stents and also may play a role in the pathophysiology of in-stent rest enosis, This study sought to investigate the expression of activation depen dent glycoproteins on platelets by flow cytometry and time until stent thro mbosis in an in vitro model of stent thrombosis. Coronary stents were place d in parallel silicon tubings with circulating citrated platelet rich plasm a to measure 1) influence of stent length on platelet antigens; 2) influenc e of heparin coating on platelet antigens; and 3) time until stent thrombos is. After recalcification aliquots of platelet-rich plasma were taken over 10 minutes in 2-minute intervals and immediately fixed and stabilized. For flow cytometric analysis monoclonal antibodies to CD41a (glycoprotein IIb/I IIa), CD42b (glycoprotein Ib-V-IX), CD62p (P-selectin), and CD63 (glycoprot ein 53) were used. Within 2 minutes after start of circulation, the express ion of CD62p and CD63 increased, Longer stents resulted in more platelet ac tivation than shorter stents (25 mm vs. 15 mm; p<0.001. Time until stent th rombosis was reduced (25 mm vs. 15 mm; p<0.05). Heparin coating did not sig nificantly influence flow cytometry detectable platelet activation but prol onged time until stent thrombosis (coated vs. uncoated; p<0.005). In contro l tubing systems without stents platelet activation was less pronounced (p< 0.0001). Antibodies to CD41a and CD42b did not show significant changes. In this model platelet activation detected by flow cytometry and time until s tent thrombosis were dependent on stent length and coating. In vitro testin g could be useful to optimize stent design and material. (C) 1999 Elsevier Science Ltd. All rights reserved.